Hidden ticket types do not display on the event page; the idea is that they can either be used for box office-specific tickets or bundled with other tickets to avoid them being purchased separately. They are also useful if you wish to issue complimentary tickets to VIPs and would like the ticket to display different information.
Hidden ticket levels can also be used for an Access code so select users with a code can have access to price levels which are not available in public.
This article outlines how to create a hidden ticket type for a specific event.
Step-by-step Instructions:
Step 1: Select the Events tab at the top of the admin panel. 
Step 2: Select the pencil (edit) button next to the event you wish to would like to create an inactive ticket type for. 
Step 3: Select Inventory on the next page.
Step 4: Select the "Add Price Level" at the top of the price level table. 